Chemical mechanical polishing is one technique utilized to process the outer surface of one or more layers formed over a semiconductor wafer. One principal use of chemical mechanical polishing is to render an outer wafer surface of a layer or layers of dielectric material to be more planar than existed prior to starting the polishing. Only some or all of the outermost layer being polished might be removed during such a process.
In chemical mechanical polishing, typically both the wafer and the pad which polishes the wafer are caused to rotate during the polishing action, typically in opposite directions. A liquid slurry is received intermediate the wafer and the polishing pad. The slurry comprises a liquid solution, typically basic, and a solid grit material, typically particles of a substantially consistent size (i.e., within 5 nanometers of the size selected from around 25 to 100 nanometers in diameter). The action of the liquid solution and grit within the solution intermediate the wafer and pad imparts removal of outer wafer layers utilizing both chemical and mechanical actions.
Although it is the intent of chemical mechanical polishing and other planarization processes to planarize a layer essentially completely flat, undesired finished topography can result depending upon the polishing conditions, the slurry and the materials being polished. It would be desirable in most instances to reduce the degree of residual topography remaining at the conclusion of a chemical mechanical polishing planarization process.